The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A nacelle generally has a tubular structure comprising an air intake upstream of the turbojet engine, a middle section designed to surround a fan of the turbojet engine, and a downstream section housing thrust reverser means and designed to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream of the turbojet engine.
Modern nacelles are designed to house a dual flow turbojet engine capable of generating a flow of hot air (also called hot flow) via the rotating fan blades, coming from the combustion chamber of the turbojet engine, and a flow of cold air (secondary flow) that circulates outside the turbojet engine through an annular passage, also called a tunnel, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two flows of air are discharged from the turbojet engine through the rear of the nacelle.
The role of a thrust reverse device is, during landing of an airplane, to improve the braking capacity thereof by reorienting at least part of the thrust generated by the turbojet engine forward. In that phase, the reverser obstructs the cold flow, and orients that flow toward the front of the nacelle, thereby generating a counter-thrust that is added to the braking of the wheels of the airplane.
The means implemented to perform this reorientation of the cold flow vary depending on the type of reverser. However, in all cases, the structure of a reverser comprises moving elements that can be moved between a deployed position in which they open a passage in the nacelle designed for the diverted flow on the one hand, and a retracted position in which they close that passage on the other hand.
These moving elements may perform a cascade function, or simply serve to activate other cascade means.
In the case of a cascade vane thrust reverser, the flow of air is reoriented by cascade vanes, associated with reverser flaps, the cowl performing only a sliding function aiming to uncover or cover the cascade vanes.
The reverser flaps form blocking doors that may be activated by sliding the cowl, causing closing of the tunnel downstream of the grids, so as to optimize the reorientation of the flow of cold air.
Furthermore, aside from its thrust reversal function, the sliding cowl belongs to the rear section and has a downstream side forming the jet pipe nozzle aiming to channel the discharge of the flows of air.
This nozzle provides the necessary power for propulsion by imparting a speed to the exhaust stream and modulates the thrust by varying the outlet area thereof in response to variations of the adjustment of the power of the engine and flight conditions.
This jet nozzle comprises a series of moving panels rotatably mounted at a downstream end of the sliding cowl.
These panels are adapted to pivot toward a position causing the nozzle section to vary.
The actuating kinematics of the cowl and such a nozzle are complex.
In fact, the nozzle being mounted on the moving cowl, the moving panels must be associated with an actuating system making it possible to drive them simultaneously and synchronously with the moving cowl during thrust reversal when the cowl moves to uncover the cascade vanes on the one hand, and to drive them, when the cowl is in the retracted position, to adapt the optimal section of the jet nozzle as a function of the different flight phases, i.e. the takeoff, cruising, and landing phases of the airplane.
Several dedicated actuating systems for responding to the particular desired kinematics of a variable nozzle and a moving cowl are known.
However, they are not satisfactory.
In fact, nacelles with a translating smooth nozzle are known in which the system for actuating the nozzle and the thrust reverser structure comprises actuating means associated with locking means.
These locking means comprise upstream locking designed to lock the thrust reverser structure on the fixed structure of the nacelle during phases for varying the nozzle section and direct jet phases.
They also comprise downstream locking designed to lock the reverser structure and the nozzle on the one hand, so as to ensure locking of the two structures during direct jet phases, and to release the nozzle from the reverser structure on the other hand, so that it translates in the downstream direction of the nacelle to increase the outlet section of the nozzle.
In this type of actuating system, to perform the thrust reversal, it is necessary to move the nozzle, then in the open position, in the upstream direction, then to lock the nozzle and the reverser structure and unlock the upstream lock to release the reverser structure and allow it to move in the downstream direction mutually with the nozzle.
However, these locking/unlocking operations take considerable time due to the many maneuvers required.
Furthermore, it has been observed that acoustic performance is decreased.